Naturally-occurring metallotetrapyrroles such as, for example, metalloporphyrins and other related metallotetrapyrroles (corrins, F430) are important cofactors in biology, where they serve as sensors,1-5 transporters,6,7 and catalysts.8-14 Synthetic metallotetrapyrroles have also found numerous industrial applications, including the catalytic oxidation of organic substrates15-19 and the fabrication of novel materials.20-22 In light of their general importance and extensive applicability, it is desirable to have new compounds which are similar in structure and function to the tetrapyrrole ligands and metallotetrapyrroles, but which also have different structural features that are advantageous.
In accordance with the present invention, new compounds which are similar and function to tetrapyrrole ligands are provided. The new compounds are designated herein as xe2x80x9ccyclic bis benzimidazole ligandsxe2x80x9d. One group of cyclic bis-benzimidazole (BBZ) ligands have the following formula: 
R1 and R2 may be the same or different;
R1 and R2 are selected from the group consisting of H, an alkyl having 1 to 10 carbon atoms, a benzyl group, a substituted 2-ethylphenyl group, a carbonyl group, a phenyl substituent, a tosyl group, and an alkylsulfonate group;
R3 and R4 may be the same or different;
R3 and R4 are selected from the group consisting of H, a methyl, and an ethyl;
R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, and R18 may be the same or different; and
R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, and R18 are selected from the group consisting of H, an alkyl having 1 to 10 carbon atoms, fluoride, chloride, bromide, iodide, nitro, amino, a carboxylate, an ester, and a phenyl group.
Preferably, the BBZ ligand is an unsubstituted, a methyl substituted, or a benzyl substituted bis benzimidazole ligand.
The unsubstituted BBZ ligand is shown below:
Unsubstituted 
The methyl substituted BBZ ligand is shown below: 
The benzyl substituted BBZ ligand is shown below: 
where
R1xe2x80x2, R2xe2x80x3, R3xe2x80x2, R4xe2x80x2, and R5xe2x80x2, are the same or different and
R1xe2x80x2 R2xe2x80x2, R3xe2x80x2, R4xe2x80x2, and R5xe2x80x2, are elected from the group consisting of H, an alkyl having 1 to 10 carbon atoms, fluoride, chloride, bromide, iodide, nitro, amino, a carboxylate, an ester, and a phenyl group.
Another group of the cyclic BBZ ligands, the reduced BBZ ligands, have the following formula 
where
R1 and R2 may be the same or different;
R1 and R2 are selected from the group consisting of H, an alkyl having 1 to 10 carbon atoms, a benzyl group, a substituted 2-ethylphenyl group, a carbonyl group, a phenyl substituent, a tosyl group, and an alkylsulfonate group;
R3 and R2 may be the same or different;
R3 and R4 are selected from the group consisting of H, a methyl, and an ethyl;
R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, and R18 may be the same or different;
R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, and R18 are selected from the group consisting of H, an alkyl having 1 to 10 carbon atoms, fluoride, chloride, bromide, iodide, nitro, amino, a carboxylate, an ester, and a phenyl group;
R19 and R20 are the same or different: and
R19 and R20 are selected from the group consisting of H, an alkyl having 1 to 10 carbon atoms, and a benzyl derivative.
These bis-benzimidazoles, in a manner similar to phthalocyanines, are useful as non-linear optical materials for use in information processing, optical switching, optical frequency conversion and telecommunications. For example, various BBZ ligands and metal complexes are useful as optical switches in fiber-optic networks or other photonic devices. The bis-benzimidazole ligands may also serve as monomeric units in organic polymers that are used in electrochemical devices such as batteries, and amperometric sensors. The bis-benzimidazole ligands are also useful as monomeric units in the backbone of polymers which are used in optical devices such as optical sensors and optical data storage devices. Chiral bis-benzimidazole ligands are useful as an affinity ligand for chiral separations.
In the metal complexes made in accordance with the present invention, a metal ion is complexed to the two benzimidazole nitrogens as well as the two schiff base/or amine nitrogens of the BBZ ligand. Essentially any mono-, di- or trivalent metal can be used for this purpose. For example, Na, K, Ru, Cs, Ca, Mg, Ba, Sr, Fe, Co, Ni, Cu, Mn, Ga, Si, Ge, Sn and Sb can be used. Preferably the metal ion is a transition metal ion, more preferably iron or manganese. The bis-benzimidazole metal complexes are catalysts useful in many organic reactions such as, for example, the epoxidation of olefins, the polymerization of olefins, atom transfer reactions and hydrogenation reaction.
The present invention also relates to methods of making the bis-benzimidazole ligands and the metal complexes thereof. These methods involve cyclizing a 2-amino or 2-nitro phenyl-benzimidazole substituted at its 4 position with an acetal or aldehyde moiety by contact with an acid. If a metal ion is present during cyclization, the ligand will coordinate around the metal ion as it forms through cyclization. If a metal ion is not present, cyclization will nonetheless occur with the benzimidazole nitrogens becoming protonated. In either case, a stable cyclic bis-benzimidazole ligand will form.
Particular methods for preparing the bis-benzimidazole involve coupling an unsubstituted or substituted phenylenediamine precursor with a substituted phenylcarboxaldehyde, or an unsubstituted phenylcarboxaldehyde, or an aldehyde . Preferably, the coupling is achieved using copper acetates as a catalyst. One method comprises the following steps: (1) reducing the benzothiadiazole group of a phenylenediamine precursor to the deprotect the diamine, (2) coupling of the phenyl diamine with an aldehyde to form a benzimidazole group, preferably via copper catalysis (3) oxidizing the benzyl alcohol group to a carboxaldehyde (4) protecting the carboxaldehyde with ethylene glycol, (5) alkylating/substituting the benzimidazole nitrogen, (6) reducing the nitro group to the amine, and (7) deprotecting the aldehyde and cyclizing under acidic conditions to provide the BBZ ligand. The metal complex is formed by refluxing the desired metal with the BBZ ligand.
A second method for forming the BBZ ligand comprises the following steps (1) coupling of a phenyl diamine with an aldehyde to form a benzimidazole group, preferably via copper catalysis (2) alkylating/substituting the benzimidazole nitrogen, (3) dibrominating the methyl group on the phenyl ring, (4) converting the dibromide to a carboxaldehyde and (5) metal/acid catalyzed reducing the nitro group and cyclizing. A third method for forming the BBZ ligand comprises the following steps (1) coupling a phenyl diamine with an aldehyde to form a benzimidazole group, preferably via copper catalysis (2) alkylating/substituting the benzimidazole nitrogen, (3) oxidation of the aromatic methyl to a carboxaldehyde, and (4) metal/acid catalyzed reduction of the nitro group and cyclizing.
The present invention also relates to method of using a BBZ metal complex to prepare an epoxide. The method comprises contacting an olefin with an oxo transfer agent or oxidant and a BBZ metal complex in a mixture comprising an aqueous or organic substrate to provide an epoxide of the olefin.